Cyclopropenoid fatty acids (CPFA) which occur in certain foodstuffs such as cottonseed oil and flour, kapok oil and okra are known to have toxic effects when consumed by animals. These unique compounds are known to impair reproduction in rats and chickens, alter the fatty acid composition in the body lipids of several species, and cause characteristic alterations in trout and rabbit liver parenchymal cells. In addition, our studies have demonstrated that CPFA act as powerful promoting agents or cocarcinogens for aflatoxin induced liver cancer in rainbow trout. This research shall have as the primary goals an explanation for the cocarcinogenic activity of CPFA, and the furthering of our knowledge of their toxic effects in trout, rats and mice. The chemical synthesis of CPFA, C14 labelled compounds, and cyclopropene derivatives will be an important objective of this study. The structural specificity required for co-carcinogenesis and effect on the metabolism of aflatoxins will be determined. The metabolic fate in animals and the effect on energy metabolism will be investigated.